The invention relates to improvements in methods for the continuous or discontinuous treatment of molten slag particularly having contents of heavy metal oxides for the recovery of valuable metals from the slag.
More particularly, the invention pertains to the treatment of molten slag with contents of heavy metal oxides for the recovery of the metal portions contained therein through precipitation or deposit during the slag melting bath or volatilization out of the slag melt.
The method employed in mechanism is different than that illustrated in German Patent D 2,306,398 entitled "Method for the Treatment of Molten Non-Ferrous Metals, Particularly Copper, through Blowing with Reaction Gases". The present invention relates to the treatment of oxidic melts or slags.
In accordance with the present invention, a jet of reaction gas is directed downwardly onto the surface of the slag to move the slag and cause a reaction between the gases and slag material. The metal bath or molten material beneath the slag is brought into induced movement by movement of the slag. The jet stream which is directed onto the upper surface of the slag, however, is not directed in such a manner as to penetrate through the slag layer and does not reach the metal bath beneath the slag but solely penetrates into the slag to form a depression a depth optimal for dynamic reasons for movement of the slag and movement of the bath therebelow.
In contrast to mechanisms and methods utilizing blowers for the recovery of steel, there is no mixture of slag and gas and metal, but the method employs a torus-type parallel flow in the slag and molten material and a reaction and heat transfer is achieved. This type of relative flow of the materials has not been utilized with methods of non-ferrous metal production or refining such as those known and used commercially as Worcra, Inco, TBRC, Mitsubishi, or with other slag-blowing methods.
In accordance with the prior teachings of the art, the separation of valuable metal contents from molten slag of predominantly oxidic low-grade concentrates, intermediary, and waste products or the like is attained by means of blowing in reaction gases horizontally into the melt and through volatilization in rotary reverberatory furnaces. If additionally non-volatilizable valuable metals are contained, processes recover these metals though treatment in a blast furnace with a hot charge. The volatilized valuable metals, such as antimony, lead, zinc, or tin occur in this method in oxidic form and are collected in filters connected in series. The residual melt consists of a concentratable slag with low valuable metal contents. The non-volatilizable valuable metals occur in a separate crude metal phase or with sufficient sulphur in a sulphide phase.
For the separation of volatilizable constituents, cyclone furnaces have also been employed.
In accordance with the method of the present invention, materials such as the following are advantageously treated: tin, lead, antimony, and bismuth-containing low-grade concentrates, particularly when they contain pyrites. Concentrates melting with difficulty may be accommodated by means of additions. Suitable intermediary products are for example, crude slags, which occur with the recovery of tin or with the preparation of copper-scrap-metal. The latter can be separated into three products, namely, tin-containing oxide mixture, raw copper and depositable and concentratable slag. Examples of waste products are tin, lead, copper-containing end-slags, tin and iron-containing waste metals or dross and zinc-containing lixiviation residues.
The invention obtains through the insuring of a reproduceable good material heat conditions which are advantageous as well as the possibilities of technically obtaining ease of regulation of operation parameters. Such parameters are nozzle pressure gas supply, nozzle spacing and gas composition and gas volume, and these can be controlled and constructed for continuous methods at favorable investment costs. The invention also offers the possibility of being utilized inexpensively in existing furnaces even if necessary with discontinuous run-offs of the process.
It is accordingly an object of the present invention to provide an improved method and apparatus for the treatment of non-ferrous slags containing heavy metal oxides for the recovery of valuable metals therefrom.
A further object of the invention is to provide an improved method and apparatus for the recovery of valuable metals from slag which can be utilized in mechanism which is readily controllable during operation, can be used for continuous or intermittent operations, can be utilized in existing furnaces, and can be adopted without substantial investment.
Other objects and advantages, as well as equivalent methods and structures, which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the description of the preferred embodiment in the specification, claims and drawings, in which: